Plural rotor impact grinding mill with cooling means



Dec. 18, 1956 B. KELLER ET AL 2,774,543

PLURAL ROTOR IMPACT GRINDING MILL WITH COOLING MEANS Filed Feb. 10, 1953 Sheets-Sheet 1 Dec. 18, 1956 KE ETAL 2,774,543

PLURAL ROTOR IMPACT GRINDING MILL WITH CQOLING MEANS Filed Feb. 10, 1953 2 s he t 2 4 ---'t: ,l I/Z 52 f 2 /7 J/ E 3 v 45 u/fi PLURAL ROTOR IMPACT GRINDING MILL WITH COOLING MEANS Bernhard Kelier, Zurich, Switzerland, and Eugene John Mayer de Berncastle, Toronto, Ontario, Canada Application February 10, 1953, Serial No. 336,167 6 Claims. (Cl. 241-55) This invention relates to grinding mills for use in connection with the grinding, pulverizing, or comminutingof various kinds of products, such as sugar, spices, dried vegetables, including grains; and, furthermore, chemicals, such as salts, resins, dyestuif, graphite; minerals, metal ores, etc.

It is an object of the present invention to provide a mill of this character in which the breaking up or pulverizing of products will be most effectively and quickly had with small power consumption.

It is another object of the invention to provide amill of very durable construction and of low maintenance cost.

It is another object of the invention to provide a mill with double-rotor construction and of maximum grinding efficiency, which results from four-fold impacts created in the space or intermediate chamber of transition from said one rotor to the other rotor, and, further, from impacts caused in and by rotor blades, ensuring a uniform and controllable pulversization of the product under treatment.

More particularly, the invention contemplates the provision of a duplex housing in which two rotors operate at the same or different and low and/or high speeds but in the same direction and against which the product is fed, thus causing impingements or impacts of the product against the blades of the rotors to thereby pulverize the product and cause it to be subsequently passed through screens of suitable mesh and thence to a discharge outlet.

The invention further contemplates improved means by which the blades of the rotors can be adjusted as to their relative positions, to thereby afford different grinding effects for various products in one and the same mill.

With these and other objects in view and hereinafter set forth, the arrangement of parts is described in the ensuing specification and delineated in the claims appended hereto.

nited States Patent In the accompanying drawings, wherein illustrative embodiments of the invention are disclosed,

Fig. 1 is a front elevational view of a grinding mill constructed in accordance with the invention;

Fig. 2 is a vertical sectional view through the mill;

Fig. 3 is a side elevational view of the mill;

Fig. 4 is a sectional view through the mill, the same being taken at right angles to that of Fig. 2 along lines 22 thereof;

Fig. 5 is a view of one of the rotors, showing the adjustable hammers or blades thereof.

Referring more specifically to the drawings, and more particularly to Figs. 1 to 4 thereof, the material to be ground or pulverized is delivered from a hopper, the outlet of which is shown at 10, through a cute 11 and into the entrance 12 of a two-branch delivery conduit 50, which has one of its branches, or that indicated at 13, in communication at its lower end with the interior of one of the grinding chambers, indicated at 14 and forming part of the housing 1. The second branch of the conduit indicated at 15, has its lower end in communication with 2,774,543 Patented Dec. 18, 1956- the interior of the second grinding chamber indicated at" 16. In the upper portion of the conduit 50 above the two branches thereof, is provided a gate 17 mounted to swing on a shaft 18 which extends across the conduit and is provided exteriorly thereof with an arm 19 having a knob 20 at its end. By manual swinging movement of the arm 19, the gate may be swung through an arc and maintained in any adjusted angular position to thereby so angularly locate the gate as to cause it to divert the flow of material into one or the other of the grinding chambers 14 or 16, or else to control the flow of the major portion of the material into one or the other of the branches 13 and 15 and hence into the grinding chamber connected thereto.

Mounted for high-speed rotative movement within the chamber 14 is a rotor 21 which consists of a hub 22 including spaced disks 40 and 41 secured on the shaft 23 and provided with a plurality of equally-spaced radially extending impact blades 24.

The lower portion of the grinding chamber 14, below the rotor 21 is closed by a foraminous screen 25 of arcuate shape to thereby provide a curved closure as the lower end of the chamber through which the ground or pulverized product will be sifted.

The housing 1 of which the chamber 14 forms a part, is provided with the second and similar chamber indicated at 16 and located adjacent chamber 14 and in communication therewith. Mounted for rotative movement within the chamber 16 is a rotor 26, which may be similar to that indicated at 21, having a hub 27 from which the radially-extending blades or hammers 28 project. Rotor 26 is mounted on the shaft 29.

The front of this two-chamber housing 1 is adapted to be normally closed by a cover plate 30 to which the two branches 13 and 15 of the feed conduit 50 are attached, and said cover plate 30 is provided with lugs 31 through which pivoted bolts 32 extend. Said bolts 32 are secured at one end to the body of the housing 1, and receive the nut-like handwheels 33 which, when threaded in place on the bolts 32, serve to hold the cover plate 30 in place at the front of the housing, yet permit the cover plate and the attached feed conduit to be readily removed when desired, for access to the rotors or for the cleaning or replacement of the screens indicated respectively at 25 and 34. The screen shown at 34 is located below the rotor 26 and constitutes the bottom of the chamber 16 and is similar in construction to that shown at 25.

Each of the rotors 21 and 26 is independently driven by its own motor, the rotors being driven in the same direction according to arrows A or B and they may be driven at the same or at different speeds. Each of the motors 35 is contained in a shell 36 provided with a plurality of vents or peripheral openings 37 through which cooling air is drawn in a manner to be explained. As will be observed in Fig. 4, the motor enclosing shell 36 includes a plurality of vent or inlet openings 37 through which fresh air is sucked by rotation of impellers 35a, connected to the motor, said air after being drawn into the motor shell passing rearwardly through the motor shell 36 and being expelled through the rear exhaust openings or vents 38 located at the rear end of the motor shell, as seen in Fig. 3. The air thus moved passes around the motor parts and assures cooling operation of the same. It will be noted that the upper portion of the housing of the mill is provided with an outer arcuate wall indicated at 39, thus providing air passages or arcuate the rear of the mill housing 1, as clearly seen in Fig. 4. Outlets or radially extending apertures 44 are provided in the lower or base portion of the housing 1 and air drawn in through the vents 37 is forced out through these outlets 44, as clearly indicated in Fig. 4. Disk 41 is provided with impeller blades 4101 which rotate therewith and aid in sucking air through axial passages 42 to cool the rotor.

When the rotors are in operation, a suction current of air is created, and the material or product to be treated is drawn down through one or the other of the branches 13 and 15 of the feed conduit to thereby enter the respective grinding chamber to which said branch of the conduit is connected, whereby the material comes into contact with the blades of the rotating rotor in the respective chamber 14 or 16. The material first impinges against the blades of the one rotor and is thrown by centrifugal force against the inner arcuate wall 14a and its inner projections 14b and then reaches an intermediate chamber space of transition 24a, 28a, which is bound at a predetermined instant by adjacent blades 24, 23 and central projection 24!), 28b. The impact through centrifugal force from predetermined parallel adjacent blades 24 and 23 becomes considerably higher (four-fold) as compared with the impact and force in each of said rotors per se. Second rotor 26 is rotated in the same direction as rotor 21. Within this intermediate chamber 24a, 28a the pieces of material hitting against opposite blades 24, 28 also impinge upon each other, thereby contributing to a reduction of said material to a predetermined degree. As disclosed and shown in Fig. 2 the peripheral distance between adjacent parallel blades of each rotor corresponds approximately to the vertical distance between the aforesaid oppositely disposed projections 24b, 28b. The blades 28 of said second rotor 26 throw the comminuted pieces of material also through impact and centrifugal force against projections 16b on inner arcuate wall 16a, so that the material is thus continuously broken up and pulverized until it is of such fineness as to enable it to pass through the sifter screens and 34 and downward out of the housing 1 for removal therefrom.

It will be noted that the aforesaid central wall projections 24b, 28b are substantially flat terminating in lateral ends to which blades 24, 28 extend and leave a relatively small running clearance thereat. The horizontal axis interconnecting the axles 23, 29 is substantially parallel to the aforesaid substantially fiat wall projections.

As the rotors operate, they also serve to draw in fresh air through the vents 37, and said air will pass around the proper motor and through the ventilating passages 38 in the motor housing, as indicated by the flow lines in Fig. 4, to finally pass out of the circumferentially spaced apertures or outlets 4S and 44.

This constant flow of air around the motor as well as around the grinding chambers assures coolness of operation of the milling apparatus. In addition, the suctional efiect secured by the rotors ensures a constant flow of the material into the apparatus, as well as the forcing of the ground material out through the sifter screens 25 and 3 3-.

in the embodiment of the invention shown in Figs. 1 to 4 inclusive, it is indicated that the blades or mallets 24 and 28 might be fixed or non-adjustable and are equally spaced from each other and arranged at an angle of about 60 to each other. In Fig. 5, a modification is shown wherein the disks 40 and 41, constituting a part of the hub of the rotor and between which blades or mallets 42s are mounted, are each provided with arcuate slots 43a in which cross bolts 442. are mounted. These bolts pivotally carry the blades or mallets 42a; and since they can be positioned at various angular locations within the arcuate slots 435., it is apparent that the relative positions of the blades with respect to one another can be accordingly changed, as required. The angularity of the blades or mallets can be changed, as may be readily understood.

From the foregoing, the operation of the improved grinding mill will be apparent. The material flowing into the mill will be drawn in pneumatically by the suctional effect created by the high speed operation of the rotors. The material thrown from one rotor to the other and into impingement against the blades or hammers of the two rotors will be rapidly and efliciently reduced to the required fiineness to enagle it to sift through the screens 25 and 34 and thus pass out of the machine. While in operation, the cooling air drawn in as described will cool the machine, and the motors and effective grinding operation is assured. By removal of the cover plate 30, which can be easily done by unthreading of the handwheels 33, the interior of the mill is at once made accessible for cleaning and replacement of screens, rotors or other parts, and a mill of long-life, freedom from breakdown, and maximum etficiency is the result.

Having described two embodiments of our invention, it is obvious that the same is not to be restricted thereto, but is broad enough to cover all structures coming within the scope of the annexed claims.

Various changes and modifications may be made Without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. In a grinding mill having a rotor with a horizontal axis of rotation, blades radially extending from said rotor, and means for driving said rotor; a housing surrounding said rotor and providing a chamber therefor, said housing including an arcuate screen positioned below said rotor defining the bottom of said chamber, an inner arcuate wall above said rotor defining the top of said chamber, an outer arcuate wall above said rotor spaced from said inner wall and provided with a plurality of circumferentially spaced apertures, a plurality of radial partitions connecting said inner and outer walls and dividing the space between said walls into a plurality of arcuate channels in communication with said circumferentially spaced apertures, respectively, said housing being provided with an axially extending central opening, said driving means extending through said central opening with clearance therebetween, a shell surrounding said driving means and connected with said outer Wall of said housing about said central opening, said shell being provided with a peripheral opening adjacent said housing and in communication with said central opening and with an exhaust opening remote from said housing, means adjacent said shell and connected with said driving means for facilitating air circulation through said shell, and further means adjacent said rotor housing and connected to said driving means for directing air circulation through said housing, whereby upon actuation of said driving means and said rotor air is automatically sucked into and through said peripheral opening, a part of said air passing through said central opening into said arcuate channels and out said radial apertures to cool said chamber, another part of said air passing out said shell exhaust opening remote from said housing to cool said driving means.

2. In a grinding mill having a housing, two rotors spaced from said other in said housing, impact blades supported by and radially extending from each of said rotors, respectively, a motor for each of said rotors, and a shaft connecting each of said rotors with its respective motor, said shafts being supported by and extending parallel to each other in said housing; said housing providing a respective chamber for each rotor, said housing including a screen positioned below said rotors and defining the bottom of the respective chamber, an inner wall in each chamber including a rear portion and a portion to which said screen is connected, an outer wall spaced from said inner wall and provided with a plurality of circumferential apertures, a plurality of radial partitions connecting said inner and outer walls and dividing the space between said walls into a plurality of channels in communication with said circumferential apertures, respectively, each rear portion being provided with a central opening directed toward the respective shaft, whereby said shafts extend through said central openings, respectively, shells surrounding said motors, respectively, and connected with said outer wall of said housing about said central openings thereof, respectively, each of said shells being provided with peripheral openings adjacent said housing and in communication with its respective central opening and being further provided with exhaust openings remote from said housing, whereby upon actuation of said motors and said rotors air is automatically sucked in through said peripheral openings of said shells, said air passing partly through said central openings, respectively, into said channels between said inner and outer housing walls and out of said circumferential apertures to cool said chambers, said air passing further partly out of said exhaust openings, respectively, remote from said housing to cool said motors, respectively and impeller blade means seated on said shafts within said motor shells and within said housing adjacent said central openings for facilitating air circulation.

3. In a grinding mill including a housing having a channeled wall, two chambers with an interconnecting space therebetween in said housing, two motors and two rotors having blades and in driving relation with said motors and mounted for rotation on respective horizontal axles arranged within said chambers; means enclosing said motors, respectively, and provided with inlet and outlet openings for the passage of ambient air through said motor enclosing means, passage means extending from said enclosing means into the channeled wall of said housing and substantially parallel to the axles of said rotors to thereby establish communication between said inlet openings, respectively, and said housing, said rotors being provided with impeller blade means radially extending from said axles into the channeled wall of said housing, impeller blade means for said motors, said housing being provided with apertures in said wall positioned remote from said chambers, respectively, and partly beyond said blades of said rotors, said rotor blades, respectively, being arranged in radially spaced relation to each other so that when said rotors rotate in the same direction blades of one of said rotors will successively be parallel to blades of the other of said rotors when said blades face each other across said interconnecting space of said chambers, whereby said rotor blades as they rotate in opposite directions relative to said interconnecting space material entrained by the blades of said one rotor is subjected to multiple impact against the blades of said other rotor, said rotation also causing ambient air to be sucked in through said inlet openings by said motor impeller means to cool said motors and further air to be sucked into said passage means by said impeller blade means for" peller blade means for moving a cooling mediuminto and through said housing of said motor means, impeller blade means for moving a cooling medium into and through said housing of said rotor means, impact blade 5 means rotatable within said housing of said rotor means,

and respective passage means extending from without into said housing of said rotor means and into said housing of said motor means and terminating in respective outlet means to thereby provide escape for said cooling medium when sucked by both said impeller blade means into the respective housings for cooling said motor means and said rotor means, said outlet means of said housing of said rotor means being positioned at a location of the respective passage means extending at least partly beyond said impact blade means.

5. In a mill according to claim 4, said rotor means including a pair of spaced rotors having substantially parallel axles, said motor means including a pair of motors operatively connected with said axles, respectively, said housing of said rotor means being provided with a pair of interconnected chambers for said rotors, respectively, through which said impact blade means move.

6. In a grinding mill having a housing with two chambers therewithin; said chambers having an interconnecting space therebetween defined by oppositely disposed substantially flat wall projections terminating in lateral ends, two rotors having respective horizontal axles mounted in said chambers, motor means for each rotor and connected to said axles for rotating both said rotors in the same direction and with substantially the same speed, said rotors being provided with radially extending impact blades arranged at an angle of about 60 with respect to each other and projecting from said rotors to said lateral ends of said wall projections, so that when said rotors turn in the same directions adjacent impact blades of both said rotors will at a predetermined instant further bound said interconnecting space of said chambers, whereby said adjacent blades of said rotors are oppositely disposed and assume a position substantially parallel to each other, the horizontal axis interconnecting said axles being substantially parallel to said substantially flat wall projections, the peripheral distance between said adjacent blades of each rotor corresponding approximate- 1y to the vertical distance between said oppositely disposed wall projections, pieces of material when entrained by said oppositely disposed adjacent rotor blades being subjected in said position of the latter to impact against said blades of both said rotors, further against said oppositely disposed wall projections, and also against each other for reducing said pieces of material to a predetermined degree.

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